The change in the shape of the tympanic membrane will be measured with Moire topography as a function of static air pressure. Its vibration patterns will also be determined using holography. Analysis of the data obtained should tell us more about the role of the T.M. shape in the middle ear function. Basilar membrane (B.M.) displacements in the inner ear of cats will be measured interferometrically at very low vibration amplitudes using a variety of conditions. A very small sensitive pressure transducer will be constructed to measure pressure acting upon the B.M. These experiments will enlarge our knowledge of inner ear function.